Efficient lead adsorption of corn straw hydrochar modified by L-arginine: Performance and mechanism

To address escalating waterborne heavy metal contamination and low utilization of agricultural waste, this study developed L-arginine-functionalized corn straw biochar (Arg-CSB) via hydrothermal treatment, leveraging the amino and carboxyl groups of arginine for surface modification. Multi-technique characterization revealed that Arg- CSB retained the native fibrous carbon skeleton of corn straw while enriching surface functional groups—notably carboxyl groups and guanidinium moieties. Adsorption experiments demonstrate selective Pb(II) binding by Arg-CSB, achieving 83.4 % removal efficiency at pH 6 and 20°C, which is double that of unmodified biochar (CSB). Kinetic analysis followed the pseudo-first-order model, indicating predominant chemical adsorption, while the Langmuir isotherm confirmed monolayer adsorption behavior with a theoretical maximum capacity of 33.29 mg/g. Furthermore, Arg-CSB demonstrated excellent stability, maintaining a 69.9 % Pb(II) removal rate after the fifth cycle experiment. This work presents a green, efficient strategy for upgrading agricultural waste into functional adsorbents, offering high-value resource recycling and targeted heavy metal remediation.